RESPONSE OF CASSAVA-MELON INTERCROP TO ARBUSCULAR MYCORRHIZAL INOCULATION AND FERTILISERS IN IBADAN, NIGERIA

Abstract

Sustainable crop production is hampered by declining soil fertility. Application of fertilisers and nutrient mobilising microbes such as Arbuscular Mycorrhizae (AM) could improve nutrient uptake and yield of crops like cassava and melon. However, there is insufficient information on the use of fertilizers and AM in cassava-melon intercrop. Hence, effects of fertilisers and AM on the yield of cassava (Manihot esculenta Crantz) and melon (Citrullus lanatus Thumb Mansf) intercropped in Ibadan were investigated. In the screenhouse, responses of two melon cultivars (Bara and Sewere) to four fertiliser treatments with (+AM) or without (˗AM) inoculation were investigated using 4×2×2 factorial arrangements. Melons were grown at one plant per 5 kg soil. Treatments were Organomineral Fertiliser-OF, Almond leaf Compost-AC, and NPK 15-15-15-(inorganic), all at 60 kgN/ha and No Fertiliser Application-NFA in a completely randomised design with three replicates. Data collected were Crop Biomass-CB (g/pot) and Fruit Yield-FY (g/pot). On the field, AM inoculation (+AM, ˗AM), fertiliser treatments (NFA, OF and NPK) and two cropping systems (sole and intercrop) were investigated. The experiment was in randomised complete block design, replicated thrice with Sewere-melon and cassava (TME-7) as test crops. Investigation on residual effects was also conducted. Data collected were Melon Seed Yield-MSY (kg/ha) and Cassava Storage Root Yield-CSRY (t/ha). Nitrogen uptake (g/kg), AM Cassava Root Colonisation-AMCRC (%) and AM Spore Count-AMSC (100g per soil) were determined. Data were analysed using descriptive statistics and ANOVA at α0.05. Bara and Sewere CB ranged from 48.8±8.0 (NFA-AM) to 168.3±4.0 (NPK+AM) and 90.0±3.2 (NFA-AM) to 213.3±4.2 (NPK+AM), respectively. Bara FY under AC+AM was 20.6±2.1 but increased significantly under OF+AM (48.3±2.4) and NPK+AM (161.7±4.0). Cultivars, AM and fertilisers significantly influenced FY and followed the order: Sewere (171.7±3.0; OF+AM) > (166.7±3.5; NPK+AM) >Bara (161.7±3.4; NPK+AM) > (20.6±2.2; AC+AM). On the field, MSY under sole was 122.0±16.4 (NFA-AM) and 499.5±25.8 (OF+AM) under intercrop. The residual effects of fertilisers and AM inoculation were significant on MSY with 178.8±22.4 under OF+AM and sole cropping followed by 159.0±15.2 under (NPK+AM) with intercrop. There was significant difference in CSRY among treatments. The CSRY ranged from 9.6±2.4 (NFA+AM) to 22.3±2.5 (OF+AM). However, interaction between fertilisers, AM and cropping systems at residual showed no significant difference among OF and NPK application without AM inoculation. The CSRY ranged from 5.4±1.3 (NFA-AM) to 11.9±2.4 (OF+AM) under sole crop. Nitrogen uptake under sole cropping ranged from 0.28±0.01 (NFA-AM) to 0.71±0.03 (OF+AM) and under intercrop, it was 0.29±0.01 (NFA+AM) to 0.42±0.02 (OF+AM). The AMCRC ranged from 35.3±0.9 (NFA–AM) to 45.0±1.6 (NPK–AM) under sole cropping system. The NFA+AM had 21.3% increase in AMSC compared to that of (NPK+AM). The interaction of fertilisers and AM had significant effect on AMSC and was in the order 35.0±1.2 (NPK+AM) < 40.0±1.3 (OF+AM) < 52.0±2.2 (NFA-AM). Organomineral fertiliser at 60 kgN/ha and mycorrhizal inoculation improved melon and cassava yields. Inorganic fertiliser reduced yield, arbuscular mycorrhizal cassava root colonisation and mycorrhizal spores under residual cropping and was therefore not sustainable.